Comparison Between Dexametidomedine\Bupivacaine and Plain Bupivacaine in Superior Trunk Block for Arthroscopic Shoulder Surgeries

This study will be conducted to investigate the efficacy of adding dexmedetomidine in STB for postoperative analgesia in patients undergoing arthroscopic shoulder surgery. * Inclusion Criteria: 1. age ;20-50 years old of both genders 2. American Society of Anesthesiologists physical status I and II 3. BMI less than 30 4. Arthroscopic shoulder surgeries. * Exclusion Criteria: 1. Patients with ASA more than II 2. Patients with a sepsis, malignancy anywhere 3. Patient with bleeding tendencies or on anticoagulation therapy 4. Patients with pre-existing neurologic deficit or neuropathy affecting brachial plexus 5. Allergy to study drugs. Study groups: The patients will be randomized into 2 groups: 1. Group DB: are administered Ultrasound guided STB with bupivacaine and dexametidomedine. 2. Group B: are administered Ultrasound guided STB with bupivacaine. Primary outcome: Duration of analgesia of Superior trunck block. Secondary outcome: 1. Cumulative dose of postoperative consumption of the rescue analgesia during 24h after STB 2. Durations of motor blockade (DOM) 3. Residual block related neurological symptoms 4. Hemodynamic variables 5. Dyspnea and sedation scale.